The internal combustion engine is a highly popular and developed machine. Great strides have been made to make internal combustion engines powerful, reliable, durable, and fuel efficient. One relatively recent development is the introduction of a windage tray that sits above the oil pan and below the crankshaft. The windage tray provides a splash barrier between the oil in the oil pan and the crank shaft. A rapidly rotating crankshaft may be slowed down by excess splash of oil which may rob the engine of horsepower. The windage tray also reduces frothing of the oil by the crank shaft and crank arms to reduce any air intake into the oil pump. Many windage trays are mounted on the underside of the engine block via bolt studs and nuts independent of the oil pan mounting. During engine assembly, the engine block is often in an upside down condition to allow the windage tray to sit in place in proximity to the crankshaft with the nuts then screwed on from above to secure the windage tray.
The use of separate mounting nuts to mount the windage tray on top of the upside down engine at the underside of the engine within the oil pan poses an undesirable risk. During installation, the underside of the engine interior is exposed there is a risk that a loose nut may be dropped into the underside of the engine during installation. If this scenario occurs, the engine may be damaged when it is turned on by the engine with its rapidly moving piston, crank arm and crank shaft banging into the loose nut. Secondly, if after installation, the nut becomes loose and separated from the mounting bolt, the nut most likely will sink to the bottom of the oil pan. However a separated nut can be shaken and again bang into the moving parts in the underside of the engine.
To eliminate the risk of a loose or separated nut, a captured nut can be pre-installed on the windage tray. Captured nuts have been known. While these captured nuts solve the problem of the nut separating from the windage tray, other problems are introduced. The washer is made from a suitable material to withstand the compression between the windage tray and the engine block. The nut however is made from a suitable material to meet both the clamp load and installation requirements. If the washer is thinner than the nut collar, and said collar is crimped over and protrudes beyond the distal face of the washer such that the crimped collar is used as the clamping surface, then the crimped collar as it is torqued into place may break apart and introduce smaller bits of loose metal into the engine interior with the same undesirable result as described above.
Secondly, the small irregular surface area provided by the crimped collar of the nut introduces the potential for clamp load loss following assembly. Those familiar with fastened joint design understand this phenomenon as “relaxation”. A smooth flat, and comparatively larger surface of a washer is desired to more accurately obtain and retain a clamp load.
What is needed is an improved captured nut that is mounted on its work piece and more particularly an improved captured nut mounted on a windage tray for an internal combustion engine.